Can body welding machine

ABSTRACT

A can body welding machine which includes a mandrel, a device for wrapping a can body blank about the mandrel, and roller electrodes for welding overlapped edges of the blank to form the side seam of the can body. A sensing device is used to control the initiation and termination of welding current flow.

United States Patent n 13,5s4,17s

Louis 11. Huber l-linsdale;

James E. Kelly, Justice; James F. McDonald; Leon M. Patarini, Chicago,all oi,1ll.

Apr. 9, 1969 June 8, 1971 National Can Corporation Chicago, Ill.

lnventors Appl. No. Filed Patented Assignee CAN BODY WELDING MACHINE 10Claims, 16 Drawing Figs.

US. Cl 219/59, 219/64 Int. Cl 823k 31/06 Field of Search 219/59, 64,

[56] References Cited UNITED STATES PATENTS 1,321,463 10/1913 Lloyd219/60 2,307,089 1/1943 Winters 219/64 2,578,832 12/1951 Pearson 219/642,635,573 4/1953 Taylor.... 219/60 3,005,901 10/1961 King 219/1313,085,146 4/1963 Ferrervela 219/60 Primary Examiner-J. V. TruheAssistant Examiner-R. Skudy Attorney Robert J. Doherty ABSTRACT: A canbody welding machine which includes a mandrel, a device for wrapping acan body blank about the mandrel, and roller electrodes for weldingoverlapped edges of the blank to form the side seam of the can body. Asensing device is used to control the initiation and termination ofwelding current flow.

PATENTED JUN 8l97l 3584', 178

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W9. 901114;, EH 5 SHEET 8 [IF 8 N l/E N T0195. LOU/5 H. HUBER, JAMES E.KELLK JAMES F. Ma DONALD, LEON M. PATAR/N/ WJ e?! 3 17: 5

CAN BODY WELDING MACHINE This invention relates to an improved can bodywelding machine in which metal can body blanks are shaped into tubularform with overlapping edges and thereafter the overlapped edges arewelded to form a continuous longitudinal side seam.

Metal cans which are formed from rectilinear blanks and which havewelded side seamsas contrasted to hammered seams are advantageousbecause they are asthetically pleasing and there is more surface area onwhich copy can be printed. The present invention provides a machine forforming welded side seams of cans in a very efficient manner.

The welding machine of the present invention includes a mandrel andmeans for wrapping a sheet metal body blank about the mandrel and forholding the adjacent'edges of the blank in overlapping relation. Meansare provided for feeding the wrapped blank to a welding station. A pairof roller electrodes are located atthe welding station for welding theoverlapping edges together along a continuous longitudinal seam thatconstitutes the side seam of the can body. The roller electrodes arepositioned on opposite sides of the seam, one of the roller electrodesbeing supported by the mandrel and the second roller electrode beingsupported by a carrier.

In the illustrative embodiment of the invention, photoelectric cells areprovided for initiating and terminating the flow of current through theroller electrodes in response to predetermined positions of the can bodyrelative to the electrodes.

Resilient means are provided for biasing the roller electrode carrieraway from the overlapped edges of the blank, and adjustable means,operable in opposition to the resilient means, are provided for biasingthe second roller electrode against the overlapped edges.

In the illustrative embodiment, the second roller electrode is driven ata lineal velocity that is greater than the velocity of the means drivingthe can blank toward the welding station. When the second rollerelectrode engages'the can blank, the blank will be advanced by theroller electrodes during the welding operation, rather than by the meansfeeding the wrapped blank to the welding station.

A more detailed explanation of the invention is provided in thefollowing description and claims, and is illustrated in the accompanyingdrawings, in which:

FIG. 1 shows a side elevational view of a body maker unit formanufacturing container bodies according to the present invention;

FIG. 2 is an enlarged side elevational view with portions brokenaway,;showing a spot welder for spot welding edge portions ofa can bodytogether to hold it during a subsequent side seam welding operation;

FIG. 3 is an enlarged end view, with portions broken away, partlyelevational and partly in section, of the spot welder of FIG. 2 takenalong lines 3-3 thereof;

FIG. 4 is an enlarged side elevational view of one embodiment of thewelding wheel assembly ofthe present invention;

FIG. 5 is an enlarged vertical sectional view, taken along lines 5-5 ofFIG. 4, showing the welding wheel assembly, support means therefor, andthe body mandrel of this invention;

FIG. 6 is a top plan view of a portion ofa welding wheel apparatus ofFIG. 4, on a reduced scale, showing driving means for the welding wheel;

FIG. 7 is an end elevational view, on a reduced scale, of the weldingwheel and mandrel portions of the welding apparatus ofthe invention;

FIG. 8 is a vertical sectional view taken along lines 8-8 of FIG. 5showing support means for the welding wheel assembly;

FIG. 9 is a top plan view of a portion of the bodymaker wings and otherelements of the invention used to form the can body;

FIG. 10 is a fragmentary end elevational view of the bodymaker wingelements of FIG. 9; v FIG. 11 is a fragmentary side elevational view,with portions broken away, showing an embodiment of the invention whichincludes a movable welding wheel and a cantilevered, fixed mandrel; H

FIG. 12 is a top plan view of the embodiment of FIG. 11 showing themovable position welding wheel and means for moving it;

FIG. 13 is a fragmentary vertical sectional view of the embodiment ofthe welder shown in FIG. 11 along line 13-13 thereof;

FIG. 14 is a vertical sectional view of portions of a bodymakermechanism for use with the welder shown in FIG. 11;

FIG. 15 is a perspective view of the mandrel shown in FIG. 14; and

FIG. 16 is a perspective view ofa portion ofthebodymaker wings shown inFIG. 14.

Referring now to FIG. I, a welding apparatus 30 is shown to comprise aplurality of stations, each of which is provided to perform a particularoperation on the can bodies. This embodiment shows a sheet feedingstation 32, a body forming and tack welding station 34, a body pickupstation 36, a side seam welding station 38, and a can body dischargestation 40. Current supply control means for supplying welding currentis provided, housed in a suitable cabinet 42, and the power supply isconnected to an output cable 44 and a current return cable 46.

The body forming and spot welding station 34 includes a spot weldersupport assembly 48, and the side seam welding station 38 includes awelding wheel support assembly 50. The individual stations will now bedescribed in greater detail.

A sheet feed station 32 is provided for advancing flat or preflexed bodyblanks to the body forming station. This sheet feeding means comprises atable for supporting body blanks and reciprocating means for advancingeach body blank separately to the body forming station. Such a feeder isdescribed, for example, in the Renard US Pat. No. 2,944,498. It will beunderstood, however, that only one feed station is necessary for usewith this invention, since, as will be discussed later, body blanks arecompletely rectangular and have no notches, slits, folds, or cutoutstherein. Thus, the Renard US Pat. No. 2,944,498 illustrates a pluralityof feed dogs moving the body through six different stations before itpresents a body to the forming horn, whereas in the present inventiononly one such station is necessary since the blanks are not notched oredged as shown, for example, in FIG. 14 of the Renard patent. Drawingsof this part of the mechanism are omitted for clarity in illustratingother parts of the invention.

At a body forming station 34, a can body B is formed by wrapping a bodyblank B around a mandrel 52 by means of body forming wings 54. As shownin FIGS. 9 and 10, the wings 54 pivot about lower shafts 56 and move upto surmount the mandrel 52 when the connecting rods 58 are moved bydriving wheels 60, as from a power gear 62. Lower wheel journals 64 andupper wing pins 66 serve as pivots for the connecting rods 58.

In use, the wings 54 converge first onto and then outwardly from themandrel 52, substantially simultaneously, except that it is preferredthat the right-hand wing 54, as shown in FIG. 10, close upon the mandrelslightly in advance of the left-hand wing, so that the lower marginaledge 68 of the blank B is in position touching the mandrel when theupper overlapping edge 70 of the blank B is moved into position. In thisway, the edges 68, 70 do not strike each other as they are being movedinto their positions surrounding the mandrel 52. As can be seen in FIG.9, the wing knives 72, that is, the outer edge portions of the wings 54,include end portions 74 and inside, recessed edges 76, so that when thewings 54 are holding a body blank in position, the end portions 74 abuteach other. The recessed edges 76 are spaced apart about a quarter of aninch, for example, so that spot welding electrodes may move downwardlyinto contact with the overlapping edges 68, 70 through the apertureformed between the edges 76.

Once the body blank Bjhas bee n positioned around the body mandrel 52,the spot welder assembly 78 (FIGS. 2 and 3) is used to spot weld theedge portions 68, 70 of the blank B together. The spot welder 78comprises a fixed vertical support member 80 attached to the body makerframe F and surmounted by a horizontal support member 82. The movableelectrode holder 84 contains a plurality (in the present instance four)of electrodes-86 ending in sharp points 88 which are each electricallyconnected by suitable cable means 90 to the holder 84. The electrodes 86are resiliently held downwardly in a desired position under theinfluence of springs 92.

Guide rods 96 are fixedly attached to the electrode holder 84 and extendupwardly through openings in the horizontal support member 82 to guideand locate the movement of the holder 84 when the piston 94 pushesdownwardly on the holder 84. The piston 94 is activated from an airsupply line 98 (FIG. 1) in which the pressure is kept at a desired levelby a regulator 100. The supply of air to the piston 94 is turned on andoff by a switch 102 which is suitably connected so as to be activated bythe movement of the wings 54 which hold the body blank B in place.

As the wings 54 assume a closed position closely surrounding the mandrel52 and wrapping a body blank tightly around the mandrel 52, and as theswitch 102 is activated, the piston 94 moves the electrode holder 84downwardly causing tips 88 of the electrodes 86 to contact the blank Bin the area where the edges 68, 70 overlap each other. The springs 92control the tension placed-on the seam formed by the overlapping edges,and afford a means of maintaining constant mechanical pressure on theseam. When the electrodes 86 contact the seam, electric switch means 104(FIG. 1) allow the passage of current which then flows briefly, forexample, for about 200 milliseconds through the lap seam and spot weldsthe body blank B into a cylindrical shape. The current, in a preferredembodiment, is about 1,000 amperes.

A body pickup and transfer station 36 comprises means for moving a canbody from the station 34 at which it is formed, to the discharge station40 at the end of the mandrel 52, in the form of an endless chain 106 onwhich are disposed a plurality of feed dogs 108. The chain is afflxed tofront and rear shafts 114 supported by bearing blocks 116 resting onbraces 118. One or more idler or tension rollers 120 may be provided forthe chain 106. A double-row roller-type construction is preferred forthe chain 106 of the invention. The dogs 108 extend upwardly into agroove 122 extending longitudinally in the mandrel 52. The chain 106 isdriven by motor means (not shown) and is designed to engage and slide acan body along the can body mandrel 52 at a desired rate. The relativespeed of the feed dogs 108 and chains 106 will be discussed furtherherein.

Referring to FIGS. 4-8, the welding station generally comprises awelding wheel support assembly 50, and a rotary electrode or weldingwheel proper 124, which is secured by bolts 126 to a rotatably mountedshaft 128. The shaft 128 rides in support bearings 130, contained insidea brass, electrically conductive outer carrier 132, which is in turnsupported by upper and lower retainers 134 held in place by locatingbolts 136. The bolts 136 secure the outer carrier 132 to the pressurepad 138, which is supported by pistons 140 operating within cylinders142 which rest upon the frame F. Inside the cylinders 142 are coilsprings (not shown) which urge the welding wheel assembly 50 upwardsagainst a downward pressure, preferably pneumatic, acting on piston 146through a cylinder 148. A desired amount of pressure is maintained inthe cylinder 148 by means of the regulator 150 connecting a pressuresupply (not shown) to the cylinder 148.

The springs inside the cylinders 142 bias the welding wheel 124 slightlyupwardly so that, for example, when the force in the line 152 reads 16pounds on the gauge 154, the actual effective force under the weldingwheel 124 is that resulting from putting 16 pounds on the cylinder 148(a 2 inch diameter cylinder, for example) which, in turn, moves the 4inch diameter welding wheel 124 downwardly against the body blank B inthe area ofthe lap seam. The edge ofthe wheel normally has a somewhatrounded edge, as opposed to a knife-type edge, the radius of curvaturethereof normally being about three thirtyseconds of an inch, it beingunderstood that some pressure is required to equalize the upward forceplaced on the pressure pad 138 by the springs contained in the cylinder142. At any rate, the force or pressure brought to bear on the lap seamis only enough to hold the edges 68, 70 in close contact and is notsufficient to amount to a forging or like operation. The four cylinders142 and pistons are designed to maintain precise alignment of the partswhen the carrier 132 and the parts associated therewith movedvertically.

The stranded ends 13? of the output cable 144 are connected to terminals137 of the carrier 132. Electrical contact between the welding wheel 124and the output cable 44 is achieved by filling the opening between therotatably mounted shaft 128 and the carrier 132 with liquid mercury, inthe space axially inside of the bearings 130, which also serve as seals.Thus, the shaft 128 is free to rotate within the carrier 132 and a soundelectrical connection is maintained, which is capable of carryingseveral thousand amperes of current. Likewise, brushes may be used tomake contact, other liquid metals or alloys may be used, or sliprings ofa silver-impregnated carbide may also be used in place of the liquidmercury.

A lower welding wheel 156 is disposed inside of the mandrel 52. As shownin FIG. 5, this wheel 156 is disposed directly beneath the upper weldingwheel 124 with the top surface of the wheel 156 extending upwardlythrough an opening 158 in the mandrel 52. Combination seal and bearingunits 160 support the shaft 162 which is integrally formed with thewheel 156. Outwardly of the ends of the shaft 162 on either side, aremercury-filled cylindrical openings 164, sealed at the end thereof byplugs 166. In this manner, electrical contact is made between the lowerwheel 156 and the mandrel 52, through the mercury in the opening 164which contacts the ends of the shaft 162. The bearing and seal units 160prevent the mercury from running into the wheel well 168. The lowerwheel assembly may also employ the substitute construction referred toabove, in place of the liquid mercury. In order to prevent possibleaccidental contact between the parts being welded and the edgessurrounding the opening 158, this area is protected by an insert of alubricous nonconductive plastic material such as a fluorocarbon polymer(Teflon). The mandrel 52 is electrically connected to the return cable46 but is preferably insulated from the rest of the machine.

The welding station 38 has leftand right-hand photoelectric cells(electric eyes) 172 and 174 (FIGS. 4 and 5) which are adapted to startand stop welding current flow from the upper wheel 124 through the bodyblank B and into the lower wheel 156. Each of the cells receives areflected beam of light from a conventional light source, preferably asource located within the same housing as each cell. The reflected beamof light changes when it is reflected from the blank, causing thephotoelectric cell resistance to change.

Thus, when the reflected beam to the left-hand cell 172 is changed dueto the position of the forward edge of the blank, a switch in thewelding current supply circuit is closed starting the flow of current,and when the reflected beam coming to the right-hand cell 174 is changeddue to the position of the forward edge of the blank, the switch isopened and the current is shut off. A new blank B breaking the beam fromthe left-hand eye" initiates a repeat cycle. The left-hand eye" isarranged so that current starts to flow substantially immediately whenthe body blank has progressed to a point directly under the center ofupper wheel 124, and the righthand eye 174 turns the current off whenthe blank B has reached an imaginary vertical centerline drawn throughthe wheel 124. During the period when the welding current is on theoverlapped edges of the blank B will pass between the electrode wheels124, 156 and weld a continuous side seam on the can body.

A single photoelectric cell could be utilized to start and stop weldingcurrent in response to the resistance change of the cell due to theposition of the forward or leading edge of the blank and its resistancechange clue to the position of the rear or trailing edge of the blank.

In some embodiments, however, there may be a small weldfree area left ateither end of the can body to reduce possible arcing and to avoidannealing the metal just outwardly to either side-of the joint, wherehead conductivity away from the weld is not good. If the metal adjacentthe seam has been unduly annealed, bending the ends of the body into aflange and body hook may cause occasional failure of the body in thisarea. It is not necessary that such weld-free area be left in mostcases, but if the weld has a tendency to anneal the metal beside theweld itself, a few thousandths of an inch of scam may be left unweldedand, provided this ultimately becomes the body hook portion of the canbody, the can will be satisfactorily pressure tight. Thus, the exactlocation of the photoelectric cells 172, 174 is, to a certain extent, amatter of preference.

Referring now to FIG. 6, it will be seen that the driving means for theupper welding wheel 124, which contacts the body blank B, and thereforedrives the lower wheel 156, comprises a welding wheel driven pulley I76driven by a belt 178 running around a driving pulley 180 rotating onshaft 182. A second drive belt 184 engages a driving wheel 186 which isdisposed at the opposite end of the shaft 182. Suitable bearing blocks188, or the like, attach this portion of the mechanism to the frame F.The second belt 184 is driven by a conventional electric motor (notshown). The sizes of the pulleys are appropriately selected so that theupper and lower welding wheels 124, 156 have a peripheral linealvelocity of between and SOinches per second.

In a preferred embodiment, the lineal velocity of the wheels 124, 156 isabout 10 percent faster than the velocity of the feed dogs 108, sincedriving the dogs 108 is fast or faster than the wheels 124, 156, tendsto cause undesirable sliding and slipping of the blank B relative to thewheels 124, 156, resulting in an inferior quality weld. Thus, it ispreferred to have the blank B advanced by the wheels 124, 156 during thewelding operation, rather than by the dogs 108. However, when the weldis completed, the dogs, which are only fractions of an inch behind thetrailing edge of the blank B, catch up therewith in a fraction of asecond and continue to advance the cylinders formed from the blank B.

FIGS. 11 to 16 inclusive show an embodiment in which a differentarrangement of can bodymaker parts is made, so that the body blankremains stationary after being formed into a cylinder and themovablewelding wheel rotates and traverses the length of the body, while thebody is being held stationary to weld the body side seam. In this case,the elements ofithe bodymaker are the'same, and a so-called crossfeedstation is used, namely one in which the body blanks are fed from oneside of the mandrel area to an area directly beneath the mandrel asdescribed above. Since such crossfeed mechanisms for bodymakers areknown in the art, they are not described herein.

Referring now to FIGS. 11 through 13, a frame member F is shown, towhich are attached a welding wheel unit 124a secured by cap screws 126ato a rotary shaft 128a housed inside a housing 132a, which is fixedlysupported by shaft cap 134a and held in place by vertical capscrews orstuds 140a. Studs 140a rest in a welding wheel carrier unit 320 whichreciprocates longitudinally on guide rods 322 (FIG. 12) secured to theframe F by mounting brackets 324. Two openings are formed in the wheelcarrier 320 which accommodate bearing units 326 of a circulating balltype for providing smooth and accurate movement of the carrier 320 backand forth over the guides 322. A double-acting pneumatic cylinder 328containing a piston rod 330 is attached to the carrier 320 by a wristpin 332 and is provided for moving the carrier 320 and the partsattached thereto back and forth. Fittings 334 are provided on either endof the cylinder 328 for admitting air thereto from hoses receiving airfrom a constant shaft 128a is run over a stationary rack 338 affixed tothe frame F by capscrews 340. A shock absorbing buffer 324 forpreventing accidental damage thereto, especially in case of failure ofthe pressure in the return side of the cylinder 328. Thus, in operation,the carrier 320 is rapidly reciprocated on the guide rods 322 causingthe wheel to be moved back and forward along a fixed axis and rotated bythe action of the gears 336, 338.

The electrical connection between the power supply cabinet 42 (FIG. 1)and the welding wheel 124a comprises the cable 44 (FIG. 1) which issubdivided into a number of strands 139a which are fastened at terminals137a by capscrews 141a wheel to the housing 132a which supports thewelding wheel 124a. Plugs 143a are provided for allowing a filling ofliquid mercury 1300 to be placed between the housing 132a and the shaft128a inwardly of the support bearings 145a which also function as sealmembers. Since the shaft 128a is always in direct electrical contactwith the metallic liquid mercury, current is carried from the cable 44to the wheel 124a and thence to the body blank B and the mandrel 52a.

The body blank receiving mandrel 52a is supported by a front block 342and a rear block 344, with the nose or end portion 346 of the mandrel52a being free from support means, or cantilevered outwardly past thefront support block 342. The support blocks 342, 344 rest on a lowerportion of the frame F. Another principal assembly is the can bodystripper, which contains an appropriate number,- say two or four,stripper bars 348 which operate in grooves 350 in the mandrel 52a andwhich are moved longitudinally of the mandrel 520 by a cylinder 352which supports the stripper bars 348. The cylinder 352 is driven by apneumatically actuated shaft 354 which is also operated from the airsupply which operates the cylinder 328.

When the wheel 124blank is passed over the outer or forward edge 346 ofthe mandrel 52a, or when the wheel 124a has finished welding the canbody and returned to the position of FIG. 11, the cylinder 352 andstripper bars 348 move forward as a unit in the grooves 350 and theleading edges of the stripper bars 348 engage the back edge of the bodyblank B pushing it off the end ofthe mandrel where it is picked up andconveyed to other equipment for flanging and end seaming, etc. Furtherdescription ofthe piston operating the shaft 354 is omitted, since theoperation is identical to the operation of the pneumatic cylinder 328,that is, the cylinder 352 and the stripper bar reciprocate as a unit inexactly the same manner as the cylinder 328 causes reciprocation of thepiston rod 330 and the carrier unit 320 attached thereto. The stripperbars 348 are somewhat longer than the can body, so that the cylinder 352which rides outside the mandrel 52a need not pass under the weldingwheel 124a even if it is in its rearmost position, that is, in theposition shown in FIG. 11.

In the operation of this embodiment of the invention it is preferredthat workflow proceed from a stack of flat body blanks through a rollpreflexer and that the blanks are then crossfed under the mandrel 52awhere bodymaker wings 54a having the action shown in FIGS. 9, l0, 14through 16 wrap them around the mandrel where they are held in positionfor the welding wheel 124a to pass over the side seam thus formed.

FIGS. 14, 15 and 16 show variations of the bodymaker components shown inFIGS. 9 and 10 and used in the embodiment of the welder shown in FIGS.11 through 13 inclusive. Referring to FIG. 14, it is desired to have aspace for the welding wheel 124a to pass over and in contact with theside seam formed by the overlap of the lower and upper edges 28a, 70a ofthe body blank B. Thus, unlike the embodiment in which the cylinder isfirst spotwelded and in which the ends of the blank may be completelysurrounded by bodymaker wings, the embodiment shown in FIGS. 11 through13 requires that the overlapped edges 68a, 70a be supported throughoutentire length, since the welding wheel traverses the entire length ofthe body while it is being held only by the wings 54a. Therefore, theouter edges of the wings 54a include front and rear locking lugs 356which engage corresponding openings 358 in the mandrel 52a. Insulationmeans 360 may be provided on the inner edges of the wings 54a to preventundesired current flow therethrough. The lugs 356 on the upper portionsof the wings 54a are shown as being integral with the wings 54a, but itwill be understood that these parts may-be made separately in order tosimplify the construction and shaping of the lugs 356 andthe openings358.

In the operation of this unit, the wing 54a and wing knife edges 362tightly clamp a body blank B to a mandrel 52a, and the welding wheell24apasses over the edges 68a, 70a of the blank B forming the plurality of.overlapping spot welds described above.

Another detail modification which is possible with the embodiment of theinvention shown in FlGS. 11-16 inclusive involves the elimination of themercury 130a which is disposed between the housing 132a and shaft 128a.If the welding wheel 124a is made relatively large, say 6 to 9 inches indiameter, for example, and the body to be welded is a beer can bodyhaving a side seam length of 4 13/16 inches, it is obvious that thewheel 124 will have an outside circumference of somewhat,

greater than 18 to 27 inches, and, accordingly, will have to rotate evenless than one-half of a complete turn while in contact with a body blankwhich is less than inches in length. Accordingly, if the strands 139a ofthe cable 44 are somewhat flexible, they may be bolted directly, as bythe screws 126a, to the welding wheel, thereby establishing directcontact between the cable 44 and the wheel 124a. Since the strands 139awill typically be large woven copper cables or straps, they will undergoseveral million cycles of moderate flexing under thesefconditions andstill deliver satisfactory performance. This construction simplifies theconstruction of the unit, decreases the cost thereof, and minimizes theelectrical resistance in the welding current circuit.

Return of the current supply to the welding wheel 124a is by way of thebus bars 364 which serve to support the mandrel 52a and which extendlongitudinally therethrough as shown in FIGS. 11 through l3. Currentflowing therethrough is returned to' the frame F of the unit either byway of a return cable, such as that shown at 46 in HO. 1, or through thesupport blocks 342, 344.

The current supplied to the weld wheels 124, 124a for the seam weldingoperation may be AC or a pulsating DC. The characteristics of thecurrent may be such as to form the seam by a number of overlapping spotwelds resulting from the pulse of current passing through the seam. Thecurrent for spot welding of the can body through the electrodes 86 maybe supplied through a transformer and controlled by relays, all in amanner known in the art.

lt is understood that the invention is not limited to the preciseconstructions herein shown, the same being merely illustrative of theprinciples of the invention.

What we claim is:

1. In a can body making machine having a mandrel for receiving a tubularbody blank with overlapped edges: means for welding said overlappededges together along a seam, said means including a first rollerelectrode in the mandrel and projecting beyond the surface thereof; asecond roller electrode; a carrier upon which said second rollerelectrode is rotatably mounted; resilient means for biasing the carrierand said second roller electrode away from said overlapped edges;adjustable means operable in opposition to said resilient means forbiasing said second roller electrode against said overlapped edges, andmeans for initiating and terminating the flow of current through theroller electrodes in response to predetermined position of the can bodyrelative to the electrodes.

2. A can body making apparatus which comprises: a mandrel; means forwrapping a sheet metal body blank about said mandrel and holdingadjacent edges of the blank in overlapping relation; means for spotwelding said overlapped edges together at longitudinally spaced regionsto hold the body in a cylindrical shape on the mandrel; means forwelding said overlapped edges together along a continuous longitudinalseam that constitutes the side seam of the can body; said seam weldingmeans'comprising a pair of roller electrodes on opposite sides of theseam, one of said roller electrodes being supported by said mandrel; acarrier; the other ofsaid roller electrodes being rotatable on saidcarrier; resilient means biasing said carrier away from the overlappededges; adjustable means operable in opposition to said resilient meansfor biasing said other roller electrode against the overlapped edges;and means for moving the spot welded body with respect to the rollerelectrodes.

3. A can body making apparatus as described in claim 2, includingphotoelectric means for initiating and terminating the flow of currentthrough the roller electrodes in response to predetermined positions ofthe body relative to the electrodes.

4. ln a can body making machine having a mandrel, body forming means forwrapping a sheet metal body blank about the mandrel and holding theadjacent edges of the blank in overlapping relationship, said bodyforming means having coacting wing members with edge portions thereofthat are spaced apart when holding said overlapped edges, a plurality ofspot welding electrodes for welding said overlapped edges together; acarriage'for supporting said spot .welding electrodes; means for movingthe carriage to position said electrodes against said overlapped edgesand in the space between said wing member portions; means on the mandreland cooperating with said electrodes for supporting said overlappededges during said welding; a first roller electrode carried by themandrel for disposition within the can body; a second carriage having asecond roller electrode for engagement with the exterior of theoverlapped edges and cooperating with saidfirst roller electrode forwelding a continuous longitudinal seam that constitutes the side seam ofthe body; feed means for advancing the spot welded body to said rollerelectrodes for engagement thereby; and means for rotating the secondroller electrode to advance the body during the seam welding.

5. In a can body making machine as described in claim 4, resilient meansbiasing said second carriage away from the overlapped edges; andadjustable means operable in opposition to said resilient means forbiasing said second roller electrode against the overlapped edges.

6. In a can body making machine as described in claim 4, photoelectricmeans for initiating and terminating the flow of current through theroller electrodes in response to predetermined positions of the bodyrelative to the electrodes.

7. ln a can body making apparatus comprising a mandrel; means forwrapping a sheet metalbody blank about said mandrel and holding adjacentedges of the blank in an overlapping relationship, said wrapping meanshaving coacting wing members with edge portions thereof that are spacedapart when holding said overlapped edges; means for feeding said wrappedblank to a welding position; means for welding said overlapped edgestogether along the seam, said welding means including a roller electrodein the mandrel and projecting beyond thesurface thereof, and a secondroller electrode; means for biasing said second roller electrode againstsaid overlapped edges; and means for driving said second rollerelectrode at a velocity that is greater than the velocity at which saidfeed means feeds said wrapped blank to said welding position, wherebyengagement of said second roller electrode with said wrapped blank willcause said blank to be advanced by said second roller electrode duringthe welding operation.

8. A can body making apparatus as described in claim 7, includingphotoelectric means for initiating and terminating the flow of currentthrough said roller electrodes in response to predetermined positions ofsaid wrapped blank relative to said electrodes.

9. A can body making apparatus as described in claim 7, the linealvelocity of said second roller electrode being about ten percent greaterthan the velocity of said feed means.

10. A can body making apparatus comprising a mandrel; means for wrappinga sheet metal body blank about said mandrel and holding the adjacentedges of the blank in overlapping relationship, said wrapping meanshaving coacting wing members with edge portions thereof that are spaceda part when holding said overlapped edges; means for spot welding saidoverlapped edges together at longitudinally spaced regions to hold thebody in a cylindrical shape on the mandrel; a first roller electrodecarried by said mandrel for disposition within the can body; a carriagehaving a second roller electrode for engagement with the exterior of theoverlap and cooperating with said first roller electrode for welding acontinuous longitudinal seam that constitutes the side seam of the body;feed means for advancing the spot welded body to the roller electrodesfor engagement thereby; resilient means biasing the carriage away fromthe overlapped edges; adjustable means operable in opposition to saidresilient means for biasing said second roller electrode against theoverlapped edges; means for driving said second roller electrode at alineal velocity that is greater than the velocity of said feed means;and photoelectric means for initiating and terminating the flow ofcurrent through the roller electrodes in response to predeterminedpositions of the body relative to the electrodes.

1. In a can body making machine having a mandrel for receiving a tubularbody blank with overlapped edges: means for welding said overlappededges together along a seam, said means including a first rollerelectrode in the mandrel and projecting beyond the surface thereof; asecond roller electrode; a carrier upon which said second rollerelectrode is rotatably mounted; resilient means for biasing the carrierand said second roller electrode away from said overlapped edges;adjustable means operable in opposition to said resilient means forbiasing said second roller electrode against said overlapped edges, andmeans for initiating and terminating the flow of current through theroller electrodes in response to predetermined position of the can bodyrelative to the electrodes.
 2. A can body making apparatus whichcomprises: a mandrel; means for wrapping a sheet metal body blank aboutsaid mandrel and holding adjacent edges of the blank in overlappingrelation; means for spot welding said overlapped edges together atlongitudinally spaced regions to hold the body in a cylindrical shape onthe mandrel; means for welding said overlapped edges together along acontinuous longitudinal seam that constitutes the side seam of the canbody; said seam welding means comprising a pair of roller electrodes onopposite sides of the seam, one of said roller electrodes beingsupported by said mandrel; a carrier; the other of said rollerelectrodes being rotatable on said carrier; resilient means biasing saidcarrier away from the overlapped edges; adjustable means operable inopposition to said resilient means for biasing said other rollerelectrode against the overlapped edges; and means for moving the spotwelded body with respect to the roller electrodes.
 3. A can body makingapparatus as described in claim 2, including photoelectric means forinitiating and terminating the flow of current through the rollerelectrodes in response to predetermined positions of the body relativeto the electrodes.
 4. In a can body making machine having a mandrel,body forming means for wrapping a sheet metal body blank about themandrel and holding the adjacent edges of the blank in overlappingrelationship, said body forming means having coacting wing members withedge portions thereof that are spaced apart when holding said overlappededges, a plurality of spot welding electrodes for welding saidoverlappEd edges together; a carriage for supporting said spot weldingelectrodes; means for moving the carriage to position said electrodesagainst said overlapped edges and in the space between said wing memberportions; means on the mandrel and cooperating with said electrodes forsupporting said overlapped edges during said welding; a first rollerelectrode carried by the mandrel for disposition within the can body; asecond carriage having a second roller electrode for engagement with theexterior of the overlapped edges and cooperating with said first rollerelectrode for welding a continuous longitudinal seam that constitutesthe side seam of the body; feed means for advancing the spot welded bodyto said roller electrodes for engagement thereby; and means for rotatingthe second roller electrode to advance the body during the seam welding.5. In a can body making machine as described in claim 4, resilient meansbiasing said second carriage away from the overlapped edges; andadjustable means operable in opposition to said resilient means forbiasing said second roller electrode against the overlapped edges.
 6. Ina can body making machine as described in claim 4, photoelectric meansfor initiating and terminating the flow of current through the rollerelectrodes in response to predetermined positions of the body relativeto the electrodes.
 7. In a can body making apparatus comprising amandrel; means for wrapping a sheet metal body blank about said mandreland holding adjacent edges of the blank in an overlapping relationship,said wrapping means having coacting wing members with edge portionsthereof that are spaced apart when holding said overlapped edges; meansfor feeding said wrapped blank to a welding position; means for weldingsaid overlapped edges together along the seam, said welding meansincluding a roller electrode in the mandrel and projecting beyond thesurface thereof, and a second roller electrode; means for biasing saidsecond roller electrode against said overlapped edges; and means fordriving said second roller electrode at a velocity that is greater thanthe velocity at which said feed means feeds said wrapped blank to saidwelding position, whereby engagement of said second roller electrodewith said wrapped blank will cause said blank to be advanced by saidsecond roller electrode during the welding operation.
 8. A can bodymaking apparatus as described in claim 7, including photoelectric meansfor initiating and terminating the flow of current through said rollerelectrodes in response to predetermined positions of said wrapped blankrelative to said electrodes.
 9. A can body making apparatus as describedin claim 7, the lineal velocity of said second roller electrode beingabout ten percent greater than the velocity of said feed means.
 10. Acan body making apparatus comprising a mandrel; means for wrapping asheet metal body blank about said mandrel and holding the adjacent edgesof the blank in overlapping relationship, said wrapping means havingcoacting wing members with edge portions thereof that are spaced a partwhen holding said overlapped edges; means for spot welding saidoverlapped edges together at longitudinally spaced regions to hold thebody in a cylindrical shape on the mandrel; a first roller electrodecarried by said mandrel for disposition within the can body; a carriagehaving a second roller electrode for engagement with the exterior of theoverlap and cooperating with said first roller electrode for welding acontinuous longitudinal seam that constitutes the side seam of the body;feed means for advancing the spot welded body to the roller electrodesfor engagement thereby; resilient means biasing the carriage away fromthe overlapped edges; adjustable means operable in opposition to saidresilient means for biasing said second roller electrode against theoverlapped edges; means for driving said second roller electrode at alineal velocity that is greater than the velocity of said feed means;and photoelectriC means for initiating and terminating the flow ofcurrent through the roller electrodes in response to predeterminedpositions of the body relative to the electrodes.